A hair fiber is composed of three major sections: cuticle (the outermost layer), cortex, and medulla. It is well understood that treatments requiring heating the hair by contact with hot surfaces damages the hair fiber. More specifically heating causes significant damage to the cuticle, or outermost layer of the hair shaft. The cuticle is composed of flattened keratinized material that is arranged in a scale like fashion. The cuticle can be further broken down into endocuticle, exocuticle, and epicuticle. For the purpose of this invention we are concerned with the protection of the epicuticle. The epicuticle is a heavily keratinized protein rich structure which is associated with lipids. It is this layer which gives hair the ability to repel water. This is the outermost layer that can be easily damaged by curling and straightening tools. The cuticle scales can be easily damaged, resulting in de-cementation and lifting, vertical cracking, shear band formation, bulges, and craters. All of the types of damage described above result in removal of portions of the cuticle exposing the inner most layers of the hair resulting in split ends, breakage and dullness of the hair fiber. Curling irons and straightening irons that come in direct contact of the hair fiber typically have surface temperatures above 150° C. At these elevated temperatures, the hair cuticle endures a significant amount stress resulting in loss of the cuticle or protective coating, thus resulting in the fiber being more hydrophilic in nature.
With each repeated heating cycle the hair becomes more damaged to the point of splitting, breaking, frizzing or just losing its luster and full body look of healthy hair. Many conditioners are sold commercially to repair or mask the affects of deleterious processes such as curling or straightening, and there is still a very strong need for a method to prevent the damage from occurring.
Currently there are several additive ingredients in the market which claim thermal protection for the hair. These additives range from silicones to plasticizers and some polymeric systems have been used to deliver or carry these materials. However, the majority of these additives can only be used under specific conditions and have poor compatibility with solvents and propellants; therefore, it is difficult to incorporate them in hair styling products such as hairsprays. Aside from additives, there are very few existing polymers which provide thermal protection to a certain extent, but these polymers are not used too often due to their lack of performance or toxicity issues. Accordingly, there still exists a need for a polymeric system that can provide the thermal protection and be applied as a hairspray or styling aid.